Radial gap electric machines typically have stator windings which are in slots defined in the stator. The windings are provided in the stator directly by a winding machine, or pre-wound around a bobbin or mandrel and then transferred to the stator. Winding is time consuming and difficult to control repeatability from one machine to the next in mass marketing. While improvements in winding design therefore proliferate to address this problem, unfortunately most result in complex winding shapes and designs, and in multi-piece windings which still must be assembled, and which introduce new issues which challenge repeatability and reliability, etc. Therefore, there remains a need for an improved method of inexpensively and reliably providing a winding in a slotted stator of a radial gap electric machine. Referring to FIG. 1, a typical permanent magnet (PM) machine according to the prior art is shown at 100. Prior art PM machine 100 has a rotor 102, with permanent magnets 104 mounted thereto by a retaining ring 106, which is mounted on a rotatable shaft 108. Rotor 102 is adjacent a stator 110 having a plurality of windings 112 interspersed between a plurality of teeth 114 mounted to a back iron 116. (For ease of illustration, the adjacent elements of windings 112 in FIG. 1b are shown unconnected.) As is well understood, PM machine 100 may operate in a generator/alternator mode or a motor mode. [When operated in a generator/alternator mode, an external torque source forces rotation of the shaft (and thus the rotor and the magnets), and the interaction of the magnets and the windings causes a magnetic flux to loop the windings in the slots. As the rotor rotates, the magnetic flux in the stator structure changes, and this changing flux results in generation of voltage in the windings, which results in an output current that can be used to power electrical devices, or be stored for later use. When operated in a motor mode, a voltage from an external source is applied to the stator windings which causes current flow in the windings and results in a magnetic flux to be set up in the magnetic circuit formed by the teeth and back iron. When current is supplied in an appropriate manner to the windings, the rotor can be made to rotate and thus produce usable torque. The operation of such machines is thus well understood.]
Such PM machines can have an “inside rotor” configuration as shown in FIGS. 1a and 1b, or an “outside rotor” configuration as shown in FIGS. 2a and 2b. The reference numerals in FIGS. 2a and 2b correspond to the corresponding features described with reference to FIGS. 1a and 1b. In the “outside rotor” configuration, however, rotor yoke 108′ replaces rotor shaft 108. For ease of illustration, the adjacent elements of the windings in FIG. 2b are also shown unconnected.
Irrespective of whether operated in an alternator or motor mode, the magnetic flux path in these prior art PM machines is as partially and simply depicted in FIG. 3, the flux path as indicated by the arrows 118, and the poles and virtual poles denoted by an “N” or an “S”. It is this magnetic flux 118 which induces a voltage in the alternator winding 112 (or in the case of a motor, creates the magnetic attraction with the permanent magnet 106 to cause rotor rotation), as described above.